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Free calculator

Use this calculator to

  • Work out the real power in kW available from a supply, generator or transformer rated in kVA
  • Convert your agreed supply capacity (ASC) in kVA into usable kW at your site power factor
  • Sense-check whether a 500 kVA transformer can support a planned kW load
  • See how improving power factor releases extra kW from the same kVA rating

kVA to kW Calculator

Convert apparent power (kVA) to real power (kW).

kVA
PF
Result
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Formulas

  • kW = kVA × PF

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Common scenarios

Select one to run it in the calculator above.

Paying for kVA your site never uses?

The gap between your agreed supply capacity in kVA and the kW you actually draw is money: capacity charges are billed on the allowance, not the usage. If this conversion shows headroom you never touch, an ASC review alongside the next retender usually recovers it, and we run both together across 30+ suppliers.

Get an electricity quoteConvert kVA to amps

Common kVA to kW conversions by power factor

kW = kVA x power factor. Most corrected commercial sites run between 0.90 and 0.95; 1.00 is the theoretical maximum where apparent and real power are equal.

SupplykW at PF 0.80kW at PF 0.90kW at PF 0.95kW at PF 1.00
10 kVA8 kW9 kW9.5 kW10 kW
15 kVA12 kW13.5 kW14.2 kW15 kW
20 kVA16 kW18 kW19 kW20 kW
25 kVA20 kW22.5 kW23.8 kW25 kW
30 kVA24 kW27 kW28.5 kW30 kW
50 kVA40 kW45 kW47.5 kW50 kW
60 kVA48 kW54 kW57 kW60 kW
80 kVA64 kW72 kW76 kW80 kW
100 kVA80 kW90 kW95 kW100 kW
150 kVA120 kW135 kW142.5 kW150 kW
200 kVA160 kW180 kW190 kW200 kW
250 kVA200 kW225 kW237.5 kW250 kW
300 kVA240 kW270 kW285 kW300 kW
500 kVA400 kW450 kW475 kW500 kW
1,000 kVA800 kW900 kW950 kW1,000 kW

For business

Why this matters for businesses

Power factor is one of the line items on a commercial electricity bill that most finance leads never look at, and that an audit will frequently find money sitting in. A site running at 0.85 power factor on a 400 kVA load is drawing 340 kW of real power and 211 kVAr of reactive power, and the supplier is charging for both. The reactive demand line on the bill, often quoted in kVArh, can be 1 to 3 percent of the total spend on a heavy industrial site, which on a £400,000 annual bill is real money for a one-off capacitor bank install.

The harder issue is capacity charges. DNO standing charges, transmission charges, and the new Targeted Charging Review banding all key off agreed capacity in kVA, not in kW. A site that has improved its power factor from 0.85 to 0.97 with a PFC retrofit can often negotiate a lower MIC band on the next contract anniversary, dropping fixed monthly costs without touching the kWh number. That kind of saving compounds over the contract life.

Purely Energy supports clients on bill audits where power factor, reactive demand, and capacity-band selection get reviewed together against half-hourly data. The conversion between kVA and kW is the foundation of that review, and the conversations usually end with either a PFC project that pays back inside 12 months, an MIC adjustment that drops standing charges, or both. Either way, the maths starts here. The portfolio-level version of the same audit, across a 20 or 50-site estate, frequently surfaces six-figure annual savings that the previous broker never bothered to look for.

Common questions

What is the difference between kVA and kW?

kVA is apparent power, the total the network must supply. kW is real power, the part that does useful work. The two are linked by power factor: kW = kVA x power factor. The gap between them is reactive power, drawn by motors, transformers and other inductive equipment to maintain magnetic fields. At a power factor of 1.0 the two are equal; at 0.8, a 100 kVA supply yields only 80 kW.

How do I convert kVA to kW?

Multiply by power factor: kW = kVA x PF. A 500 kVA transformer feeding a site at 0.8 power factor can deliver 400 kW of real power; raise the power factor to 0.95 and the same transformer supports 475 kW. This is why power factor correction is often cheaper than upgrading a supply when a site is running out of capacity.

What power factor should I use if I do not know mine?

Measure rather than guess where you can: half-hourly meter data or your supplier portal usually shows kW and kVA side by side, and dividing one by the other gives your actual power factor. As a rough engineering guide, motor-heavy industrial sites often sit around 0.8, mixed commercial loads around 0.9 to 0.95, and modern IT or LED-dominated loads close to unity. The calculator lets you test the sensitivity in seconds.

Why is my agreed supply capacity in kVA rather than kW?

Because the distribution network is constrained by current, and current follows apparent power, not real power. The DNO must size its cables and transformers for the full kVA your site draws, including the reactive component, so capacity is agreed and charged in kVA. A site with a poor power factor uses up more of its agreed capacity for the same useful kW, which is why correcting power factor can defer a costly connection upgrade.

Can kW ever be higher than kVA?

No. Power factor is at most 1.0, so real power can never exceed apparent power; kW equals kVA only for a purely resistive load such as an electric resistance heater. If a conversion appears to show kW above kVA, either the power factor has been entered as a percentage (use 0.95, not 95) or the two readings were taken at different times.

Related calculators

The conversions that procurement and engineering use alongside this one.